Elastomeric yarn



Feb. 16, 1965 E. v. MARTIN 3,169,363

ELASTOMERIC YARN Filed Feb. 14, 1963 EMMETT l! MART/IV INVENTOR.

ATTORNEYS United States Patent 3,169,363 ELASTGMERIC YARN Emmett V. Martin, Kingsport, Tenn, assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed Feb. 14, 1963, Ser. No. 258,479 2 Claims. (Cl. 57152) This invention relates to elastomeric yarn, and more particularly to a composite elastomeric yarn having an elastic core covered with one or more helical windings of a relatively fine denier yarn.

It is known to provide elastomeric yarns comprising an elastomeric core having a covering thereover. The coverings generally comprise a helical winding of a relatively fine denier yarn around the elastomeric core. The covering controls the stretch of the composite elastic yarn, and in addition may provide improved appearance, better hand and protection for the elastic core against perspiration, grease and the like.

In covering the elastomeric core, the core yarn is usually stretched considerably during the covering operation, and the covering yarn is wound on the core at a rather high helix angle. When the covered yarn is released from tension, it contracts in length until it jams against the cover yarn or has no tension. When the yarn is extended, the core contracts within the helix of the cover, first making the cover loose and, as the yarn is extended further, the helix again tightens against the core providing a stop at the upper limit of elongation. Within the operational range of elongation, the composite elastomeric yarns of the prior art have generally had an irregular appearance due to looseness of the covering yarn along the length of the core. It therefore appeared desirable to overcome this problem of looseness of the covering in composite elastomeric yarns. One object of my invention is to provide elastomeric yarns having a helically wound cover over an elastomeric core, which cover remains snug throughout the range of elongation of the yarn. A further object of my invention is to provide composite elastomeric yarns having greater elongation than is achieved with the elastomeric yarns of the prior art. Other objects of my invention will appear herein.

These and other objects of my invention are accomplished by an elastomeric yarn having a substantially Y-shaped cross section and a helically wound cover thereover. I have found that the covers of composite elastomeric yarns in accordance with our invention do not tend to become loose at any point within the range of elongation. I have also found that the composite elastomeric yarns in accordance with the invention have an elongation of 25-50% greater than is attainable with a similar core and cover, but which core has a circular cross section of equal denier to the Y-shaped core.

My invention will be further illustrated in the accom panying drawings. FIG. 1 shows a cross section of a Y-shaped monofilament in accordance with my invention. FIG. 2 shows a Y-shaped monofilament having a helically wound yarn cover 11 thereover.

The improvement achieved by the present invention will be demonstrated in the following examples. Example 1 shows a typical composite elastomeric yarn of the prior art having a helically wound cover over a round core, and Example 2 shows the improvement achieved by employing a Y-shaped core.

Example 1 A polymer was formed from dimethyl terephthalate, 1,4-cyclohexanedimethanol and poly(tetramethylene glycol) having a molecular weight of 2,200. This polymer,

which contained 77% by weight poly(tetramethylene glycol), was melted at 265 C. and extruded at the rate of 4.5 lbs. per hour through a circular jet into air at room temperature. After traveling 5 inches through air, the monofilament entered a bath of water at about 1 C., traveled vertically downward 5 inches through the water, passed around a roll and upward through water for 18 inches. After a heat-setting treatment with free relaxation for 5 minutes in air at 140 C., the filament had an elongation of 560%.

The sample monofilament was processed on a rubbercovering machine at a draft ratio of 4.121. Top and bottom spindles were each equipped with a N0. 7 fiyer wire. The bottom spindle was operated at 9500 r.p.m. and the top spindle at 8500 r.p.m. The monofilament was covered to a stretch of 220% off the machine, with both top and bottom covers consisting of 20 denier, 6 filament nylon. The bottom cover had a helical twist rate of approximately turns per inch, and the top covering had approximately 85 helical turns per inch. The yarn thus obtained had undesirable looseness of the cover within its range of elongation.

Example 2 The same procedure was followed as in Example 1 except that instead of extruding the polymer through a circular orifice, a Y-shaped orifice was employed to produce a Y-shaped monofilament having the same denier as the round monofilament of Example 1. When this monofilament was covered as in Example 1, the resulting covered yarn showed no tendency for the cover to loosen within the range of elongation of the yarn. Moreover the elongation was approximately 30% greater than with the composite yarn of Example 1.

The composition of the Y-shaped elastomeric core may be any of those employed in the art heretofore. A highly useful polymer for this purpose is the linear high polymeric elastomeric polyester described in the copending application of Bell, Kibler and Smith, Serial No. 215,768, filed August 9, 1962.

The Y-shaped elastomeric core may be covered in accordance with my invention with a single covering of the yarns previously used for this purpose in the art. I have found that nylon covers give highly useful results. One or more covers may be applied to the Y-shaped elastomeric monofilament core; however, I prefer to apply two helically wound covers wound in opposite directions. The double covering reduces or eliminates twist liveliness that is sometimes present when only one cover is employed.

The Y-shaped configuration of the elastomeric core of the composite yarns essentially consisting of three lobes is preferably substantially symmetrical and the lobes of the core preferably are substantially the same shape. As shown in FIG. 1, the distance cd of the tip preferably is equal to or greater than the length ab of the base, but should be at least 0.4 of the length ab.

However, various modifications may be made in the configuration of the Y-shaped filaments of the invention without impairing their function in the present inventive combination. For example, the size of the lobes of the Y-shaped filament need not be absolutely straight nor must they define a smooth curve. Thus, the sides may curve slightly inwardly or outwardly and various other distortions may be introduced while still accomplishing the objects of the invention.

The composite elastomeric yarns in accordance with my invention may be employed to produce a wide variety of fabrics. They may be used alone or in combination with other yarns to produce wearing apparel such as swim suits, brassieres, girdles, elastic bandages and gen erally those applications wherein elastomeric properties are useful or desirable.

The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understoodthat variations and modifications can be effected within the spirit and scope of the invention as described hereinabove' and as defined in the appended claims. 7 1

I claim:

1. A composite elastomeric yarn comprising an elastomeric core composed of a polymer formed by condensing dimethyl terephthalate, 1,4-cyclohexanedimethanol and poly(tetram'ethylene glycol), saidelastomeric core essentially consisting of three lobes ina substantially Y-shaped configuration, the lobes of said coreihaving a tip-to b'ase 4- ratio of at least 1 to 1 and being substantially symmetrical and of essentially the same shape; and, said core having a helically Wound fine denier yarn cover thereover.

2. Claim 1 wherein the helically Wound fine denier 5 yarn cover is composed oi nylon.

References Cited in the file of this patent UNITED STATES PATENTS Lathem et al Dec. 3-1, 1963 

1. A COMPOSITE ELASTOMERIC YARN COMPRISING AN ELASTOMERIC CORE COMPOSED OF A POLYMER FORMED BY CONDENSING DIMETHYL TEREPHTHALATE, 1,4-CYCLOHEXANEDMETHANOL AND POLY(TETRAMETHYLENE GLYCOL), SAID ELASTOMERIC CORE ESSENTIALLY CONSISTING OF THREE LOBES IN A SUBSTANTIALLY Y-SHAPED CONFIGURATION, THE LOBES OF SAID CORE HAVING A TIP-TO-BASE RATO OF AT LEAST 1 TO 1 AND BEING SUBSTANTIALLY SYMMETRICAL AND OF ESSENTIALLY THE SAME SHAPE; AND, SAID CORE HAVING A HELICALLY WOUND FINE DENIER YARN COVER THEREOVER. 